Size and Shape Control of SrTiO₃ Particles Grown by Epitaxial Self-Assembly

Cubic SrTiO 3 particles are obtained by precipitation from an aqueous gel suspension. The gel suspension is prepared by hydrolyzing a TiOCl 2 solution with NaOH and adding SrCl 2 . The addition of citric acid leads to spherical particles. The particle size can be tailored in the range 80−1400 nm by varying the temperature and the concentration. A careful control of the synthesis conditions is essential for producing particles with a narrow size distribution. The results of HRTEM and ED investigations provide strong evidence that the oriented aggregation of small (4−5 nm) nanocrystals is the dominant growth mechanism for the formation of the observed SrTiO 3 particles. The primary nanocrystals self-assemble in a highly oriented fashion, producing defective single-crystal particles. The above results show that the directional aggregation process can be controlled by changing the temperature and concentration of the suspension as well as by adding organic molecules, obtaining SrTiO 3 particles with a controlled size and shape.